I did some investigating on this one. Is the problem occurring while also using improved invisibility? Evidently there's a game bug that allows someone under this greater sanctuary and improved invisibility to be targeted by enemies (link).

Nothing has changed about the basic functionality of the spell (the hardcoded "ethereal" effect), so I'm thinking this may be to blame.

I have seen this only very rarely with Archers. Sometimes they seem to be 'locked on' to my PC so that even when I throw up GS, they still shoot at me. Its intermittent and rare, however, and probably an engine issue.

What would be nice, though, is if the commoners would stop shouting my name when I am moving around on another dimension

The community 1.70 or 1.71 patch has a fix for this issue I think (GS+invis), not sure if it fixes any issues with NPCs targetting players with just GS....

Which is a still present bug.

My pure-class sorc does not have any invisibility spells, only GS, and has been nailed a number of times by melee attacking NPCs while under GS. Prior to getting improved combat casting, the AoO's while casting under GS (defensive spells, not attack spells which do drop the GS... after being cast though) were the big issues for me.